Radio receiving apparatus



July 14, 1931. s. TARZlAN RADIO RECEIVING APPARATUS Filed Dec. 31, 1926 ll l'illlul llilrfilh A M aw 4. ATTORNEY.

Patented July 14, 19,31

ma ma-m OFFICE sA'BKns 'rARzIA-N, or PHILADELPHIA, PENNSYLVANIA, ASSIGNOR To ATWATER} KENT iii MANUFACTURING coMrnNY, or PHILADELPHIA, rENNsYLvANIA, A CORPORATION or PENNSYLVANIA Application filed December 31,1926.

My invention relates to radio receiving apparatus, and more particularly to more or less compact receiving sets utilizable for the reproduction of speech and music transmitted at any of the wave lengths Comprised within a broadcasting range.

There customarily intervenes between the antenna or equivalent absorption structure and the input circuit or electrodes of a thermionic device of the three-electrode or audion type a circuit tunable by a variable react ance, as a variable condenser, whose movable or rotatable element it is desired shall be, to gether with the cathode or filament of the thermionic device, connected to earth or equivalent; it is further customary or desira-ble to effect stabilization or neutralization of the thermionic device, particularly when utilized as avradio frequency amplifier, and for such purpose, in some systems, the input element is connected to the grid of the thermionic device and to a point between which and the cathode of the thermionic device, or

earth or equivalent, to which the cathode is connected, there exists a substantial difi'erence of alternating or fluctuating potential. In such an arrangement if the tuning device were directly associatediwith the input element, that is, were connected in a circuit or path between the grid and the aforesaid point, the adjustable element of the tunin device would be at a potential materially dif ferent from that of earth or the cathode.

{in accordance with my invention the input element is an inductance or winding, connected between the grid and the aforesaid point,

and serves as the secondary of an input transformer whose primary circuit is insulated from said secondary and is tunable by a variable reactance, preferably a condenser, whose adjustable element or. rotor is con nected to earth, or equivalent, together with the cathode of the thermionic device, with the result that thetuning action on the part of the operator introduces no disturbance notwithstanding the fact that the input ele ment is connected to a point whose alternating or fluctuating potential is materially higherthan that of earth or equivalent. Furthermore, were the tuning condenser directly RADIO RECEIVING APPARATUS Serial No. 158,175.

associated with the input element, as when connected between the grid of the thermionic device and the aforesaid point, one armature or plate of the condenser would exhibit P through the insulation necessarily involved a considerable capacity with respect to earth and with respect to the cathode connected to earth and such capacity would in association with reactance between the aforesaid point and the cathode make more difficult the neutralization or stabilization of the thernnonic device; and in addition the insulation of the tuning condenserin such case would introduce mechanical difliculty and additional expense.

Further in accordance with my invention the aforesaid input element proper, as the aforesaid secondary coil or winding, is smaller, as an absorber of radio frequency energy,

vice is minimized, and, in addition, the aforesaid secondary or input element is preferably disposed within the primary winding or coil in the tuning system or circuit, whereby the inputelement or secondary is shielded by the primary. a

My invention resides in the system of the character hereinafter described and claimed.

Foran understanding of my invention and for an illustration of one of the various forms it may take reference is tobe had to the accompanying drawings in which:

Figure 1 isadiagra n of a receiving system embodying my invention.

Figure 2 is a sectional View of a portion of a transformer utilized in my system.

Referring to Fig. 1, the electro-radiant energy transmitted by various transmitting stations, as broadcasting stations, is absorbed by the antenna D between which and the earth or counter capacity E is connected the primary P of a radio frequency transformer. It will be understood, however, that other types of energy absorbing. structures or circuits may be employed, including loop or coil antennae or socalled frame aerials.

V, V1 and V2 are three-electrode thermionic devices or audions utilized as radio frequency amplifiers. Each comprises as usual a filament or cathode f, a grid or equivalent control electrode g, and an anode or plate a. These devices and their associated circuits constitute the radio frequency amplifying system, which, while indicated as comprising three stages, may comprise one or other suitable. number of stages.

This radio frequency amplifying system may be aperiodic or non-selective in that the output circuit or circuits and the following input circuit or circuits are untuned or substantially aperiodic, transferring or responding with substantially equal facility to oscillations of all the frequencies within a predetermined range, such as a broadcasting range.

Intervening between the antenna D and the radio frequency amplifying system is the highly selective system comprising the cascaded tuned, resonant or selective circuits S, S1 and S2, comprising, respectively, the pairs of inductance coils and variable tun ing condensers L, G, Ll, C1 and L2, C2.

Such a cascaded system of two or more resonant circuits is of the character and mode of operation of'the cascaded tuned circuits disclosed in' prior Letters Patent to Stone, No. 714,7 56, December 2, 1902, in that it ef fects tuning in geometric progression, yielding high degree of selectivity or exclusion of the energies of those transmitting stations which operate at wave lengths different from that of a particular wanted station.

. Of the selective circuit S the inductance L is coupled to the transformer primary P in the antenna path. This coupling may be close whereby tuning of the circuit S efiects to substantial degree a tuning of the antenna path. This coupling P, L be fixed, or, as'indicated by the arrow, variable for control of volume of the music, speech or messages reproduced.

The inductances or coils L, L1 and L2, each of which may be wound in a single layer, may be the. sole or major part of the inductance of each of the circuits S, S1 and S2. The first and third coils L and L2 are disposed with their axes substantially at right angles to each other whereby the magnetic coupling between them is ubstantially nil. The coil L1 has its axis disposed at an angle to the axes of both coils L and L2 and is in consequence effectively magnetically coupled with both, operating as a secondary with respect to the coil L, and as a primary with respect to the coil L2.

The coupling effected by the system oescribed is cascaded in the sense that energy is transferred by magnetic coupling from the circuit S to circuit S1, and from the latter to S2 without direct coupling effect of the circuit S upon circuit S2.

The coupling between the coils L and L1, and again betwen L1 and L2 is preferably very loose and may be of the order of one per cent or of such low magnitude which will at once yield high selectivity and effect high or optimum magnitude of current induced in each secondary circuit.

This system, of the character of the afore said Stone patent, gives particularly good results in radio telephony for the following reasons:

In the case of two similar coupled circuits, each tuned to resonance, it can be shown that the coefficient of coupling for maximum current in the secondary circuit is equal to the reciprocal of the ratio of reactancc (either inductive 'or capacity) to the circuit resistance. In well designed circuits of low resistance and in the broadcast range this ratio is a hundred or more, so that the optimum coupling is of the order of one per cent or less. The system will have two resonant frequencies which are spaced apart by an amount which in percentage is equal to the coeificient of coupling. With the present broadcasting frequencies ranging from 550 to 1500 kilocycles and with a coupling of about one per cent the spacing will be 5.5 to 15 lrilocycles. The effect of the two resonant peaks so close together is to flatten or render uniform the transfer over a range of this order while beyond on either side the transfer falls off rapidly. This behavior, inherent in the system of the aforesaid Stone patent, is ideal for the reception of radio telephony in which, for quality, it is desirable to transmit a'band of frequencies of, say, ten kilocycles and in which, for selectivity or separation of different transmitting stations, it is desirable that the transfer fall off rapidly on either side. The use of three coupled circuits permits similar results, only the cut-off on either side is still sharper givgreater selectivity. The resultant high qualityof reproduction, particularly clearness of speech, is very noticeable with this system over systems of equal selectivity in which this band effect does not occur.

As indicated in Fig. 1, one armature 9 of each of the tuning condensers C, C1 and C2, whoseother arma-tures are indicated atlO, is connected to earth or counter capacity E. Preferably these armatures 9 are the rotors or adjustable elements.

While the rotors or adjustable elements 9 of the tuning condensers C. G1 and C2 may be independently adjusted and each provided with a separate knob and dial, the rotors 9, and especially those of condensers C1 and C2, of the tuned circuits remote from the antenna, may be mechanically coupled to effect single dial control and operation.

Closely coupled to the inductance L2 of the third tuned circuit S2 is the winding or inductance L3 in the grid or input circuit of y the first-radio frequency amplifier tube V. As indicatedin Fig.2, the winding- L3 may be, disposed Within the winding L whereby the'latt er more or less completely shields the coil L3 rem direct capacitative coupling with the antenna D or prevents coil L3 from being otherwise affected by the received en ergy than by way of the tuned circuits S, S1 andSQ. 1

The output circuits of the radio frequency amplifier tubes V, V1 andVQ- are coupled to the input circuits oftheradio frequency amplifier tubes V1 and V2 and the detector tube V3 by the radio frequency transformers T, T1 and T2, which may be aperiodic or' untuned in he sense that their primary and secondary circuits are aperiodic or untuned, whereby they do not effect selectivity, which function is performed entirely by the two or more cascaded tuned circuits S, S1 and S2. i

To stabilize the radio frequency amplifiers V, V1 and V2, there may be employed any suitable meansor system for counteracting the coupling effected by the grid to plate capacity of each, to prevent regenerationor th development of self-oscillations. I v

In the example illustrated, in the circuit of each of these amplifiers are provided the capacities or condensers K and K1 (or'equivalen-t impedances or rcactances) forming, in effect, balanced VVheat-stone bridge in one arm of which is the capacity between grid and anode a and in another arm of which is the capacity between the grid 9 and the cathode f. Connected from grid to filament ofv each of these tubes is a high resistance r, which, with the aforesaid. condensers, forms aneutralizing system of the character disclosed in Patent No. 1,787,732,,January' 6, 1931,.to John M. Miller. I v ,7 neutralizing system of this character, 0: its equivalent,is esscntialin connection with radio frequency. amplifying systems. The use of a neutralizing system of special advantagein connection withthe type of amplifier herein described inasmuch as it assists effecting high and uniform amplification over. a broad band of frequencies. To attain this result it is desirable: to keep theelfective capacities ofthe coupling transformers at a minimum. It is Well known that the input capacity of a vacuum tube amplilier is increased by the presence of a load in the plate circuit. This capacity would be additive to the capacity ef the coupling transformers such as T and T1 of Fig. 1, and hence tend to diminish the range which could be effectively covered. Vfhen neutralization is employed this. enhanced ca pacity is eliminated and the range is very much improved.

The secondary of the transformer T2 is connectedto the grid and'cathode of the detector or demodulator tube V3 in whose grid leadis connected the usual grid'condenser K2. In the example illustrated, the usual high grid leak resistance is connected from grid to a suitable point upon the resistance /1 connected across the terminals of the filament in the output circuit of the detector tube V 3 is the primary, shunted by the condenser K3, of the audio frequency coupling trans: former T3 whose secondary is connected in the grid circuit of the audio frequency amplifier tube V 4 whose output circuit is coupled by the audio frequency transformer T4 with the input circuit of, the audio frequency amplifier tube V5 in whose output circuit is connected the signal translating instrument I which may be a telephone, loud speaker, or equivalent. I

The anode circuits of the several tubes V-V5 are supplied with current from the source of current or battery 13; the cathodes are heated by current from the source or batteryA; and a source or battery Gr may be povided for negatively biasing the grids of one ormore of the tubes as may be suitable or desirable. A condenser K4, of relatively hi 'h capacity is provided for by-passing radio frequency currents,.particularly around the battery B. p

In the neutralizing or balancing arrangement associated with the tube V the input element or winding L3 is connected to the grid gof the tube V and to the point 0, which lat ter is at a substantial alternating or fluctuat ing difference of potential from the cathode f of the tube V and from the earth E or equiv alent.

If the grounded tuned circuit S2 were sub stituted for the winding L3, the point 0 would in effect bebrought to earth or cathode potential, so rendering the balancing reactance K inelfective and rendering the balancing or bridge system inoperative.

But if the circuit S2 were notgrounded and were connected in place of the winding L3, as would bethe more natural procedure, there would exist a substantial alternating difference of potential between this tuned circuit and earth or cathode. Furthermore, in such an arrangement the rotor 9 of the tuning condenser would be at a substantial alternating potential difference from earth or the cathode. Furthermore, and particularly, were the tuning condenser directly associated with the input element L3, between one armature or plate of the condenser and earth or the cathode would exist, because of the insulation necessarily involved, a considerable capacity which in association with the reactance K, or its equivalent, between the point 0 and earth or cathode,.make more difficult the neutralization or stabilization of the circuits of the "amplifier tube V because militating against simplicity and ease of establishment of balance of the neutralizing bridge or circuit. In addition the need for insulation of the tuning condenser in such case would also introduce mechanical complication and additional expense in manufacture.

By an arrangement such as shown, however, a point in the tuned circuit S2, as the rotor 9 of its tuning condenser C2, may be connected to earth or the cathode, and by coupling the additional winding or coil L3 to the winding L2 all the foregoing difliculties and disadvantages are overcome.

In a system of the character illustrated, there is a tendency for the received energy directly to impinge upon or affect the input circuit or grid of the tube V, or for the absorption structure or antenna D to be capacitatively coupled with said input or grid, and in either case this is undesirable becau e the selective system, comprising one or more of the circuits S, S1 and S2, is less efifective in excluding unwanted stations. This undesired effect is reduced by the arrangement indicated because the input element or system of the tube V may be materially smaller, as a capacity absorption net work, than the combination of inductance L2 and con denser G2 which if substituted for the winding L3 would be to a greater degree directly affected by the absorption structure or antenna or the electro-radiant energy. The undesirable eiiect of this character is further reduced by placing the secondary coil or input element L3 within its primary L2 whereby it is shielded by the winding L2 with consequent reduction of direct action upon the input ele ment or system of the tube V and accordingly in efiect enhancing the selectivity obtainable by the cascaded tuned circuits;

It is characteristic of a system of the type disclosed that a tuned circuit which it is desired shall be grounded, together with an electrode, such as the cathode, of a thermionic device, is coupled to an input element which is connected to another electrode of said thermionic device and to a point which is at a substantial alternating difference 01" potential from the first mentioned electrode, such as the cathode.

What I claim is:

1. Radio receiving apparatus comprising absorption structure, a plurality of cascaded tuned circuits operatively related to said structure, means for grounding said tuned circuits, a three-electrode thermionic device, and an untuned input circuit therefor including an input element coupled to one of said tuned circuits and connected to the grid and to a point between which and the cathode there exists a substantial alternating potential difierence.

2. Radio receiving apparatus comprising absorption structure, a plurality of cascaded tuned circuits operativelyv related to said structure, means for grounding said tuned circuits, a three-electrode thermionic device,

an untuned input circuit therefor including an input element coupled to one of said tuned circuits and connected to the grid and to a point between which and the cathode there exists a substantial alternating potential difference, and means for grounding said cathode.

3. Radio receiving apparatus comprising absorption structure, a plurality of cascaded tuned circuits operatively related to said structure, a three-electrode thermionic device, an untuned input circuit therefor including an input element coupled to one of said tuned circuits and connected to the grid and to a point between which and the cathode there exists a substantial alternating potential difference, and means for connecting said tuned circuits and said cathode to each other.

4. Radio receiving apparatus comprising a thermionic device, a tuned circuit comprising a variable condenser and an inductance, an untuned input circuit including an input element connected to the grid and to a point between which and the cathode there exists a substantial alternating difference of potential, and electro-magnetically coupled solely to said inductance, and a connection from the movable armature of said condenser to earth.

5. Radio receiving apparatus comprising a thermionic device, a tuned circuit comprising a variable condenser and an inductance, an untuned input circuit including an input element connected to the grid and to a point between which and the cathode there exists a substantial alternating difference of potential, and electro-magnetically coupled solely to said inductance, and a connection from the movable armature of said condenser to said cathode.

6. Radio receiving apparatus comprising a thermionic device, a tuned circuit comprising a variable condenser and an inductance, an untuned input circuit including an input element connected to the grid and to a point between which and the cathode there exists a substantial alternating difierence of potential, an electro-magnetically coupled solely to said inductance, and a connection to earth from said cathode.

7. Radio receiving apparatus comprising a three-electrode thermionic amplifier, a circuit arrangement for preventing retroactive effect upon the grid, said circuit arrangement having a point between which and the cathode there exists a substantial alternating difference of potential, a transformer secondary connected to said point and to the grid, and a grounded tuned circuit connected to earth and including the primary of said transformer.

8. Radio receiving apparatus comprising a three-electrode thermionic amplifier, a circuit arrangement for preventing retroactive efi'ect upon the grid, said circuit arrangement having a point between which and the cathode there exists a substantial alternating difference of potential, a transformer secondary connected to saidpoint and to the grid, and a tuned circuit connected to said cathode and including the primary of said transformer.

9. Radio receiving apparatus comprising a three-electrode thermionic amplifier, a circuit arrangement for preventing retroactive effect upon the grid, said circuit arrangement having a point between which and the oathode there exists a substantial alternating difference of potential, a transformer secondary connected to said point and to the grid, and a tuned circuit connected to said cathode and to earth and including the primary of said transformer.

10. Radio receiving apparatus comprising an absorption structure, a three-electrode thermionic amplifier, a plurality of cascaded tuned circuits intervening between said structure and said amplifier, a circuit arrangement for preventing retroactive effect upon the grid of said amplifier, a point in said circuit having an alternating potential substantially different from the cathode potential, the secondary of a transformer connected between said point and said grid, one of said tuned circuits including the primary of said transformer, each of said tuned circuits including a variable condenser whose movable element is connected to earth.

11. Radio receiving apparatus comprising an absorption structure, a threeelectrode thermionic amplifier, a plurality of cascaded tuned circuits intervening between said structure and said amplifier, a circuit arrangement for preventing retroactive effect upon the grid of said amplifier, a point in said circuit having an alternating potential substantially different from the cathode potential, the secondary of a transformer connected between said point and said grid, one of said tuned circuits including the primary of said transformer, each of said tuned circuits including a variable condenser whose movable element is connected to said cathode.

12. Radio receiving apparatus comprising an absorption structure, a three-electrode thermionic amplifier, a plurality of cascaded tuned circuits intervening between said structure and said amplifier, a circuit arrange-' ment for preventing retroactive efiect upon the grid of said amplifier, a point in said circuit having an alternating potential substantially different from the cathode potential, the secondary of a transformer connected between said point and said grid, one of said tuned circuits including the primary of said transformer, each of said tuned circuits including a variable condenser whose movable element is connected to earth and to said cathode.

13. Radio receiving apparatus comprising a thermionic device having anode, cathode,

and control electrodestructure, an .untuned input circuit therefor including an input'element both terminals of which'are of alternating' potential substantially differing from the potential of the cathode of said device, a connection from aterminal of said element to the ccntrolelectrode of said device, a tuned circuit comprising a variable condenser and an inductance coupled to said input'element, and a'connection from the movable armature of-said'condenser to said cathode.

14. Radio receiving apparatus comprising a thermionic device having anode, cathode, and control electrode, an untuned input circuit therefor including an input element both terminals of which are of alternating potential substantially differing from the potential of earth, a connection from a terminal of said element to the control electrode of said device, a tuned circuit comprising a variable condenser and an inductance coupled to said input element, and a connection from the movable armature of said condenser toearth.

.15. Radio receiving apparatus comprising a thermionic device having anode, cathode, and control electrode, of an untuned input circuit th-erefor'comprising an input element connected to said control electrode and to a point between which and the cathode there exists substantial difference of alternating potential, atuned circuit comprising an inductance closely coupled to said input element and a variable condenser, and a second tuned circuit comprising an inductance loosely coupled to said first inductance and a variable condenser in shunt thereto.

16. Radio receiving apparatus comprising a plurality of cascaded tuned circuits, each comprising a variable condenser and an inductance, a connection of negligibly small impedance between the movable armatures of said condensers, thermionic devices, and untuned input circuits therefor including input elements therefor connected to grids of said devices and to points oetween which and said connection there exists substantial difference of alternating potential, the inductance of one of said tuned circuits and the input element of the associated thermionic device constituting respectively the primary and secondary windings of an input transformer.

17. Radio receiving apparatus utilizing a thermionic tube, an untuned input circuit therefor including an input inductance both terminals of which are of alternating potential substantially differing from that of the cathode of said tube, and a grounded closed circuit tunable to effect selection of radiofrequency signal energy and comprising an inductance coupled to said input inductance for transferring selected radio-frequency energy to said untuned input circuit.

18. Radio receiving apparatus utilizing a thermionic tube, an untuned input circuit therefor including an input inductance both terminals of which are of alternating potential substantially differing from that of the cathode of said tube, a closed circuit tunable to effect selection of radio-frequency signal energy and comprising an inductance coupled to said input inductance for transferring selected radio-frequency energy to said untuned input circuit, and a connection from a terminal of said closed tunable circuit to the cathode of said tube.

' SABKES TARZIAN.

CERTIFEGATE OF CORRECTION.

July 14, 1931.

Patent No. 1,814,774.

SARKES TARZIAN.

cation of the certified that error appears in the printed speciti tion as iollews: Page 3, line 89, for line 113, claim 6, for

above numbered patent requiring correc the misspelled word "povided" read provided; page 4,

"an" read and; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in'the Patent @itice.

Signed and sealed this 12th day of July, A. D. 1932.

it is hereby M. J. Moore, Acting Commissioner of Patents.

(Seal) 

